Photothermographic film generally includes a base material, such as a thin polymer or paper, typically coated on one side with an emulsion of dry silver or other heat sensitive materials. Once the film has been subjected to photostimulation (exposed), for example, by light from a laser of a laser imaging system, the resulting latent image is developed through application of heat to the film. To produce a high quality image, controlling heat transfer to the photothermographic film during the development process is critical. If heat transfer is not uniform, visual artifacts such as non-uniform density and streaking may occur.
Several types of thermal processors have been developed in efforts to achieve optimal heat transfer to exposed photothermographic film during processing. One type employs a rotating heated drum having multiple pressure rollers positioned around a segment the drum's circumference to hold the film in contact with the heated drum during development. Another type of processor, commonly referred to as a flat-bed processor, employs multiple transport rollers spaced to form a generally horizontal transport path that moves the photothermographic film through an oven. Both the heated drum and the transport rollers of the flatbed processor have surfaces which may be coated with a thin polymer coating which contacts and assists in transporting the photothermographic film through the processor during development.
As the photothermographic is heated during development, some types of emulsions produce gases that include contaminants which can condense and become deposited on surfaces within the processor. Over time, these and other contaminants can accumulate on the polymer-coated surfaces of the drums and rollers and potentially cause visual defects in the developed image. Consequently, the processors require regular cleaning to remove such deposits from the surfaces of the drums and rollers.
During the cleaning process, a qualified technician generally applies solvents to the surfaces of the drums and rollers to dissolve and remove the deposits. However, due to inherent variations in such a procedure, one portion of the surface of a drum or roller may be more thoroughly cleaned than another portion of the surface during a single cleaning process, and the thoroughness of the cleaning may vary from one cleaning process to the next. Such variations in the cleaning process can result in inconsistencies in the quality of the images produced by the thermal processors. Such a cleaning process can be also be costly and result in processor downtime, and solvents employed in the cleaning process sometimes produce undesirable odors, resulting in complaints from customers and technicians alike. Furthermore, in situations where an entire drum is replaced, associated heaters must be recalibrated in order to operate properly.
It is evident that there is a need for improving thermal processors, particularly drum type processors, to reduce problems associated with routine maintenance.